ctr-task.go

package main

import (
	"bytes"
	"context"
	"fmt"
	"sync"

	"github.com/containerd/containerd"
	"github.com/containerd/containerd/containers"
	"github.com/containerd/containerd/mount"
	"github.com/containerd/containerd/namespaces"
)

var (
	Root            = "/var/lib/containerd"
	State           = "/run/containerd"
	RuntimeEndpoint = "/run/containerd/containerd.sock"
	DebugEndpoint   = "/run/containerd/debug.sock"
	imageName       = "docker.io/library/alpine:latest"
)

func main() {

	ctxo := context.Background()
	ctx := namespaces.WithNamespace(ctxo, "tasktest")
	client, err := containerd.New(RuntimeEndpoint, containerd.WithDefaultNamespace("tasktest"))
	if err != nil {
		fmt.Println("Client Create", err)
		return
	}

	//Create
	c := &containers.Container{
		ID: "test-task-ctr2",
	}

	specs, err := containerd.GenerateSpec(ctx, client, c)
	if err != nil {
		fmt.Println("Spec Gen", err)
		return
	}

	var wg sync.WaitGroup
	wg.Add(2)

	rootMount1 := make([]mount.Mount, 1)
	rootMount1[0].Options = make([]string, 1)
	rootMount1[0].Type = "overlay"
	rootMount1[0].Source = "overlay"
	rootMount1[0].Options[0] = "workdir=/var/lib/test/work,upperdir=/var/lib/test/upper,lowerdir=/var/lib/test/lower1"

	rootMount2 := make([]mount.Mount, 1)
	rootMount2[0].Options = make([]string, 1)
	rootMount2[0].Type = "overlay"
	rootMount2[0].Source = "overlay"
	rootMount2[0].Options[0] = "workdir=/var/lib/test/work,upperdir=/var/lib/test/upper,lowerdir=/var/lib/test/lower2"

	fmt.Println(rootMount1)
	fmt.Println(rootMount2)
	ctr, err := client.NewContainer(ctx, "test-task-ctr2", containerd.WithSpec(specs, containerd.WithProcessArgs("sh", "-C", "/start.sh")))
	if err != nil {
		fmt.Println("Container Create", err)
		return
	}
	defer ctr.Delete(ctx)

	executeTask(ctx, ctr, rootMount1, &wg)
	executeTask(ctx, ctr, rootMount2, &wg)
	wg.Wait()
	return
}

func executeTask(ctx context.Context, ctr containerd.Container, rootMount []mount.Mount, wg *sync.WaitGroup) {
	defer wg.Done()
	stdout := bytes.NewBuffer(nil)

	//NewTask
	task, err := ctr.NewTask(ctx,
		containerd.NewIO(bytes.NewBuffer(nil), stdout, bytes.NewBuffer(nil)),
		containerd.WithRootFS(rootMount))
	if err != nil {
		fmt.Println("Error in NewTask: ", err)
		return
	}
	defer task.Delete(ctx)

	//Wait
	statusCh, err := task.Wait(ctx)
	if err != nil {
		fmt.Println("Error in TaskWait: ", err)
		return
	}
	//Start
	if err := task.Start(ctx); err != nil {
		fmt.Println("Error in Start: ", err)
		return
	}

	//event
	fmt.Println("waiting for Task")
	status := <-statusCh
	//exit.

	fmt.Println("Event Recieved!!!", status.ExitCode())
	if status.ExitCode() != 0 {
		fmt.Println("process returned non-zero exit code: ", status.ExitCode())
	}

	fmt.Println("Output: ", stdout.String())
	return
}